1. Field of the Invention
This invention relates to the field of temperature controlled vehicle bodies, and particularly to semi-trailers with a refrigeration unit, ducts and a false ceiling structure.
2. Summary of the Invention
In the field of temperature controlled vehicle bodies and more particularly refrigerated semi-trailers it has been long recognized that the promotion of air circulation greatly enhances the efficiency of the temperature controlling operation. This invention relates to the use of ducts and a false ceiling structure to maximize efficient circulation of air and minimize intrusions in the cargo area or areas.
While this invention is primarily designed for refrigerated semi-trailers, it equally applicable to other cargo carrying structures such as shipping containers, railroad cars and the like and would relate to any temperature control situation whether the temperature of the cargo is to be elevated or lowered. Further the preferred embodiment is adapted to use in a multiple compartmented vehicle however it would also enhance air circulation in a vehicle with a single compartment.
Numerous advantages are provided by the configuration disclosed herein.
One object of the invention is to provide a ceiling structure which has fewer projections, corners or edges extending into the compartment.
Another object of the invention is to provided greater control in the airflow into the first compartment of a compartmentalized semi-trailer permitting a greater degree of control over the location of hot or cold spots on the cargo carried in the compartment.
Another advantage from the greater degree of control in addition to control over the direction of airflow is the greater degree of control over the quantity of airflow providing greater control over the temperature in the compartments generally.
Another object of the invention is in improvement in the efficiency in airflow direction resulting from the sealing of the entire series of refrigerated air duct work, the minimization of the placement of obstructions in the air current and avoidance of turbulence causing members.
Another advantage to the invention is the use of transition elements utilizing relatively straightforward sheet metal forming techniques which permit adaptation to alternative refrigerator units having integral ducts through substitution of a single sheet metal formed first transition element without significant loss in efficiency as opposed to unconnected or unsealed prior art configurations.
Another advantage to the invention is that the placement of parts movable to control airflow can be made so as to more closely align those parts with the direction of airflow further increasing efficiency and reducing turbulence.
Another advantage to the invention is that more accurate temperature control is possible because the higher degree of control over the leakage of refrigerated air around or past prior art air deflection mechanisms.
Another advantage of the invention is that an integral sealed false ceiling and duct work configuration favorably contributes to the overall strength and insulation and properties of the trailer roof structure.
Another advantage to an integral sealed configuration is that it is less prone to become soiled through the entry of materials, particulate or the like into the central refrigeration duct system because it is under pressure and is not generally open to the first compartment generally as are prior art funnel type or deflector type configuration.
Another advantage to the invention is that build up of frost or ice is less likely then in prior systems because projections into the refrigerated air current are reduced in number and components are aligned more closely parallel to the direction of flow.
Other advantages will become apparent upon on further reading of the specification.
3. BACKGROUND OF THE PRIOR ART
The funtion of providing variable or adjustable control over air flow in refrigerated semi-trailers can be performed by varied structures including at its simplest a fabric duct work attached to the ceiling with spaced removable fasteners providing for adjustment of the air flow by the simple expedient of unfastening selected fasteners thereby permitting air to spill out of the duct work at a predetermined position.
The invention relates to the use of substantially rigid duct work providing air passageways. In this art there are essentially three types of arrangements or devices used to control air flow. These arrangements are bleed air valve devices, air flow restriction devices and air flow diverting devices.
The first mentioned controlling devices operate in conjunction with passageways in which pressurized air flows. By opening valves air is permitted to flow from within the pressurized passageways out of the passageway into a cargo compartment. A series of valves provides greater selectivity in terms of directing air to desired locations in a single compartment or into selected separated compartments.
An example of bleed air refrigerated semi-trailer flow control is disclosed in U.S. Pat. No. 2,677,244 issued to Wehby May 4, 1954. This patent utilizes L section ducts opened to a refrigeration compartment in which dry ice is placed with a fan circulating the air through the duct and with rotating vane type valves permitting the selective direction of air from the pressurized duct into a compartment in which the direction of refrigerated air is desired. Return air is moved through a corresponding L shaped duct placed in the opposite top corner from the pressurized duct.
Flow diverting devices or mechanisms are placed within a storage compartment and present a face surface at an angle to an air current in the compartment as will discussed in connection with U.S. Pat. No. 4,531,377 and art cited therein. Flow diverting devices present at least one edge around which the air current is permitted to flow into the compartment itself. These diverting plates may be presented at an angle greater than, equal to or less than perpendicular to the direction of the air current and change the direction of at least a portion of the air current caused by aerodynamic forces caused by the substantially flat body placed in an air current.
An item of prior art which contains this type of air flow control is revealed in U.S. Pat. No. 4,531,377 issued to Zajic Jul. 30, 1985. As will be noted herein this prior art also uses the air diverting type of control. Further the file wrapper for Zajic reveals yet another prior art structure which also uses the damper type control and the air diverting type control. Moving an open damper into a closed position increases resistance to the air flow within the confines of the passageway or duct. Accordingly pressure is increased on the upstream side and the pressure difference between upstream and downstream sides is also increased, thereby decreasing the volume of cooling air available to be directed into any compartment or portion of a compartment downstream of the damper. The air flow diverting plate in Zajic constitutes a hinged plate hinged at its edge most remote from the source of refrigerated air with its edge nearest the source of refrigerated air being adjustably supported so as to select a desired angle relative the direction the flow of a current of air passing from the refrigerator unit into the chambers in which the structure is located. The hinge is placed at the bottom of duct work which is connected to the damper previously described. Because of the duct work and the velocity of the air current and the returns interconnected with the ducts and compartments, a portion of air in the air current from the refrigerator unit will be carried through the duct system. At such time as the pressure downstream the diverting plate equals that upstream the air will, however, flow around the forward most edge and directly into the first compartment.
The Polar American trailer prior art drawing which is contained in the file history of the Zajic patent also utilizes a flow diversion plate, although this structure is hinged from the roof of the trailer.
Another item of prior art is a false ceiling refrigerated stripping container made by assignee Trailmobile, Inc. in approximately 1972 utilizing a false ceiling structure with a funnel-like air current directing structure near the refrigerator unit outlet. This provided a straight through passage way to the rear of the container, having no flow regulation structures. The air current directing structure had no moving parts or adjustment.
Air flow restriction devices or means operate within a passageway in control air flow by obstructing air flow through increasing the surface area presented to the air flow as it flows through a passageway of fixed area. Typically these devices constitute dampers pivoting about a transverse axis presenting substantially an edge of a plate to the air flow when in an open position and presenting substantially the flow face of a plate in a close position with intermediate positions being selectable.